On 13 October 2017 at 09:28, Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx> wrote: > Am Thu, 12 Oct 2017 11:37:26 +0100 > schrieb Dimitri John Ledkov <xnox@xxxxxxxxxx>: > >> zipl from s390-tools generates root=/dev/ram0 kernel cmdline for >> zfcpdump, thus BLK_DEV_RAM is required. >> >> zfcpdump initrd mounts DEBUG_FS, thus it is also required. >> >> Without above two options kernel images built with zfcpdump_defconfig >> fail to perform zfcpdump. Affects v4.10+. >> >> Bug-Ubuntu: https://launchpad.net/bugs/1722735 >> Bug-Ubuntu: https://launchpad.net/bugs/1719290 >> >> Cc: stable@xxxxxxxxxxxxxxx >> Signed-off-by: Dimitri John Ledkov <xnox@xxxxxxxxxx> >> --- >> arch/s390/configs/zfcpdump_defconfig | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/arch/s390/configs/zfcpdump_defconfig b/arch/s390/configs/zfcpdump_defconfig >> index afa46a7..04e042e 100644 >> --- a/arch/s390/configs/zfcpdump_defconfig >> +++ b/arch/s390/configs/zfcpdump_defconfig >> @@ -27,6 +27,7 @@ CONFIG_NET=y >> CONFIG_UEVENT_HELPER_PATH="/sbin/hotplug" >> CONFIG_DEVTMPFS=y >> # CONFIG_FIRMWARE_IN_KERNEL is not set >> +CONFIG_BLK_DEV_RAM=y > > In https://launchpad.net/bugs/1722735 was reported that the ramdisk > problem was introduced with kernel 4.10. But to me it looks like > the kernel config option CONFIG_BLK_DEV_RAM is also not there in > kernel 4.9: > True. The actual symptoms on v4.10 is that /dev/ram0 does not exist. And I guess BLK_DEV_RAM is one way to get it working once again. I did a checkout of v4.9 generated zfcpdump_config; did a checkout of v4.10 generated zfcpdump_config and diffed the two, grepping for removed keys which points at $ diff -u v4.9 v4.10 | grep '^\-' | grep =y -CONFIG_DEVKMEM=y Which is from commit e334cd69fa65fc9e916d6adc8d860a9b6b9e7281 Author: Dave Young <dyoung@xxxxxxxxxx> Date: Mon Oct 10 13:34:33 2016 +0800 Move CONFIG_DEVKMEM default to n I will retest again a v4.10 kernel with just CONFIG_DEVKMEM toggled back to y. As an end-user of kernel config it feels surprising that toggle of /dev/kmem controls whether or not initrd is available to be used as root=/dev/ram0. I would have thought CONFIG_BLK_DEV_INITRD=y should be sufficient to get initrd available as /dev/ram0. If all that checks out, what would the preference be DEVKMEM=y or BLK_DEV_RAM=y to guarantee that booting with `root=/dev/ram0` works (which is what `zipl -d` generates), irrespective of any other kernel defaults changes? -- Regards, Dimitri. -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
